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Riparian Planting Effectiveness Monitoring

Background

Many areas of the state have identified the lack of healthy streamside vegetation as one of the limiting factors related to the decline of water quality and fish habitat. In the 1990’s before OWEB was a state agency, many riparian planting and fencing projects were implemented under the Watershed Health Program and Governor’s Watershed Enhancement Board (GWEB). These riparian restoration projects were designed to improve riparian vegetation conditions and thus help restore water quality and fish habitat. Riparian planting projects use native shrubs and trees to stabilize stream banks, displace invasive species, provide stream shade, and provide habitat and food sources for fish and wildlife species. Mature trees that fall into the stream also provide hiding and resting places for fish and other aquatic species. Riparian fencing projects are designed to exclude livestock, and in some cases wildlife, from riparian areas when overuse is potentially damaging to sensitive stream banks and the stream bed.

In 2009, OWEB contracted with Demeter Design, Inc. (DDI) to conduct a retrospective analysis of a representative sample of riparian restoration and fencing projects in basins located in the South Coast and Grande Ronde areas of Oregon.

Effectiveness monitoring for riparian restoration and fencing projects evaluates the current riparian vegetation structure and seeks to determine whether these projects still exist on the landscape and are meeting the original objectives to a) increase riparian cover and stream shade, b) reduce livestock pressure on the riparian area, and c) reduce stream bank erosion and increase stream bank stability.

In cooperation with watershed councils, soil and water conservation districts, and other local partners, DDI collected field data at 77 projects implemented by GWEB between 1995 and 1998. Lack of well-defined project locations in original project plans resulted in DDI being able to locate and gain landowner permission on less than 20% of the total implemented projects. Projects were compared to the riparian vegetation conditions on the opposite side of the stream from the project location, or to local “reference stream reaches” which reflect a minimally disturbed condition.​

Analysis of data from the completed projects indicates:

  • Completed project sites have less riparian canopy cover compared to local, reference stream reaches.
  • Completed projects sites have similar riparian shrub and tree species as the local, reference stream reaches but are not yet mature enough to provide increased stream shade in the South Coast.
  • Compared to the opposite stream side, riparian vegetation conditions on completed projects is generally similar. In the South Coast, there was increased percentage of grasses and forbs on the project site which may lead to an exclusion of invasive species.
  • Riparian fencing status was evaluated on 49 completed projects and had a failure rate of 83% in the Coquille basin and 54% in the Grande Ronde. Causes for failure include flood and windfall damage, removal, or lack of maintenance.
  • Many original project plans lacked well-defined project locations which meant there was not enough information to locate the project sites.
  • Continued maintenance of riparian plant establishment and fencing may need to be evaluated over time to ensure project success.

This information will help guide future riparian planting and riparian fencing projects and provides a good starting point for evaluating other areas of the state for these restoration actions over time.

OWEB has developed better ways to achieve plant establishment goals and devoted resources for plant maintenance to help ensure increased survival and growth rates.

OWEB is also providing GIS and information management tools for grantees to use when reporting on completed projects. This should increase accuracy and accountability in project tracking and reporting.​

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